Apparatus for forming films and coatings



mil in} 148. c. s. FRANCIS, JR 2439,02

APPARATUS FOR FORMING FILMS AND COATINGS Filed Jan. 2, 1945 2Sheets-Sheet 1,

April 20, 1948 c. s. FRANCIS, JR 7 ,8@

APPARATUS FOR FORMING FILMS AND COATINGS Filed Jan. 2, 1945 2Sheets-Sheet 2 Patented Apr. 20, '1948 UNITED STATES APPARATUS FORFORMING FILMS AND COATINGS Carleton Shurtlei'f Francis, In,

West Harwlch, Mass.

Application January 2, 1945, Serial No. 571,048

11 Claims. (01. 91-43) This invention relates in general to coating andfilm casting and, in particular, to an apparatus for coating sheetmaterials, and for producing self-sustaining films; The inventionrelates further to correlated improvements in coating and film coatingapparatus designed to increase the efilciency and to extend the uses ofsuch apparatus.

Various devices have been employed heretofore for coating sheetmaterials and for casting films on temporary supports. In one priordevice, a coating composition was applied to one surface of paper orother sheet material by feeding the composition through a wick whichmade contact with a surface of the sheet material. Coating by means of awick is limited, however, to the use of liquids of extremely lowviscosity. more particularly to aqueous liquids which readily wet thewick and which can be drawn through it without change in composition.

When an attempt is made to use a wick with a multi-componentcomposition, for example, an organic film-forming material, and aplasticizer, dissolved in a volatile organic liquid, it has been foundthat the solvent evaporates at the surface of the wick, resulting in agelling of the composition at the surface, while the solvent migratesfaster than the other ingredients through the center of the wick.Accordingly, it has been found impractical to use a wick for coating andfilm casting such multicomponent compositions and in particular for anycomposition of high viscosity. A wick is also impractical for producingcoatings or films of any substantial thickness or with compositions ofhigh viscosity.

On the other hand, it has been proposed to coat paper on one side bybringing the paper into contact with the surface of a body of liquid.However, such devices require special means for preventing the liquid orcoating composition from running around the edge of the sheet to becoated. In one such prior device the point of contact of the sheet withthe liquid is in a horizontal plane, whereupon the liquid tends to dripfrom the coated surface, resulting in streaks and non-uniform films orcoatings.

If an attempt is made to pass a sheet to be coated vertically through aslit in a rigid walled reservoir, micromatic adjustment of the slitopening is necessary to prevent leaking and it is impossible to coatrough or uneven materials by such devices.

In a third method heretofore employed by the prior art, sheet materialsare coated on one or both sides bv use of a doctor blade or a knife,

the clearance between the edge of the blade or knife and surface of thepaper determining the thickness of thefilm or coating produced there-'with. Here again it is necessary to use micromatic adjustments on theknife in order to make thin films. It has been found, however, that suchdevices are impractical where the liquid is one of low viscosity orwhere it is a composition containing a rapidly volatile solvent. Withlow viscosity liquids, the liquid tends to flow around the edge of theknife, and frequently it does not spread uniformly over the sheetmaterial. On the other hand, with a composition containing volatileliquids, the evaporation of the solvent in front of the knife or bladeresults in a change in viscosity, and the deposition of the film orcoating has a greater percentage of solids at the end of the run than atthe beginning. Rough surfaced materials can not be coated uniformly bymeans of a doctor blade.

Accordingly, it is a general objectof the present invention to providemeans for forming films with a liquid film-forming material of uniformthickness.

It is another object of the invention to provide an apparatus forcoating sheet materials and for casting thin films on suitable materialswhere the thickness of the film is not a function of any mechanicalmeans and is independent. therefore, of the mechanical configuration ofthe coating applicator, and is free of errors resulting from humanjudgment.

It is another object of the invention to provide an apparatus forforming films which permits a wide variation in thickness of the filmand in the speed of operation without alteration in the composition ofthe coating or film so produced.

It is another object of the invention to provide an apparatus forsimultaneously applying a film to one surface of a temporary support andfor transferring the film from such support to the surface of materialto be coated.

It is another specific object to provide an apflexible weir formed byone ervoir, wherein the level of the film-forming liqof the wall, sothat the edge of the flexible wall liquid overlying the top contacts thefilm-receiving surface and adheres thereto, due to surface tension.

The apparatus of the invention comprises, in combination a liquidreservoir having at least one flexible liquid-retaining wall which formsthe weir and means for passing a surface to be coated, such as a drumsheet, or endless band, upwardly in contact with and beyond the upperedge of the-flexible wall, and means to maintain the level of the liquidin said reservoir above the top edge of such wall, so that the liquidoverlying the upper edge of the wall contacts the film-receiving surfaceand adheres thereto, by surface tension.

One of the paramount features of the present invention resides in theprovision of a flexible wall for the liquid reservoir which will lie incontact with and automatically conform to irregularities in the surfacebeing coated, primarily as a result of the resiliency of the wall itselfand, in the preferred form of the invention, as a result of thehydrostatic pressure of the liquid in the reservoir exerted against theinside surface of the flexible wall acting to force said wall outwardlyinto firm contact with the surface being coated, to follow allvariations therein from a true fiat plane and thereby produce aresilient fluid-pressurized surface-conforming seal against saidsurface, whereby leakage of the liquid downwardly past the upper edge ofthe weir formed by said flexible wall is efllciently prevented.

In one embodiment of the apparatus, there is provided. in addition tothe above, means for bringing a second sheet material into contact withthe coating before or after it is dried, and means for applyingpressure, with or without heat, to cause the film to bond the two sheetmaterials together, thus producing a composite laminated article.

In a third embodiment, there is provided means for bringing a sheetmaterial to be coated into contact with the sheet carrying the film,before or after the film has been completely dried, and applyingpressure, with or without heat, to cause the film to adhere to thesecond sheet material,

and means for stripping the first sheet from the film so transi erred.

For a more complete understanding of the another embodiment of theinvention;

Fig. 3 is a diagrammatic sectional elevation of a third embodiment ofthe invention;

Fig. 4 is an enlarged sectional elevation of the coating head shown inFigs. 1, 2 and 3;

Fig. 5 is a perspective view, partly in section, of the essentialelements of the coating head shown in Fig. 4;

Figs. 6, 7 and 8 are sectional views, similar to Fig. 4, illustratingmodified forms of coating heads capable of use in practicing the presentinvention and Figs. 9, 10 and 11 are diagrammatical sectional viewssimilar to Figs. 2 and 3, showing further embodiments of the invention.

flexible wall of a res- Y ing purposes, it is applicable for coating anyfiexible sheet material such, for example, as paper, textile fabrics,felts, leather, metal foils, and organic plastic films of all kinds. In.particular, it is applicable for forming thermoplastic transfers whichcomprise a temporary support in the form of a flexible sheet materialand a thermoplastic film temporarily supported thereon and which iscapable of being stripped from the support after the application of heatand pressure. Such thermoplastic transfers are described and claimed inU. S. Patent No. 2,3 3,717. The apparatus is also applicable forapplying adhesive coatings to sheet materials preparatory to lamienating.

The apparatus of the invention is applicable for forming films fromliquids, solutions, emulsions and molten plastic materials in general.Accordingly, the invention is adapted for the formation of films fromaqueous solutions of cellulose xanthates, water-soluble andalkali-soluble cellulose ethers, gelatin, casein, zein, glue, starch,dextrin, polyvinyl alcohol, rubber latex, and the like, or fromsolutions in organic solvents of synthetic resins as a class, cellulosederlvatives as a class, synthetic and natural rubber, and mixturesthereof or molten masses or emulsions of such organic plastic materials.When thermosetting resins are used they maybe converted to the infusiblestate during the hardening of the film. 1

Referring to Fig. 1, there is shown one embodiment of the apparatuscomprising, incombination, a horizontal rotatable drum I of largediameter which, if desired, may be provided with suitable heating meansof conventional type. The liquid L to be formed into a film is containedin the reservoir 2, the reservoir having at least one longitudinalflexible side wall 3 which presses against the peripheral surface A ofthe drum I, and is held in surface conforming contact therewith by thehydrostatic pressure of the liquid contained in the reservoir. Theliquid in the reservoir is maintained above the top edge of the flexiblewall so that the liquid contacts the peripheral surface A of the drum I,above the upper edge of the flexible wall 3 and is drawn upward by thesurface A in the form of a thin layer.

The layer of the liquid L which clings to the surface A is convertedinto film F on the surface A of the drum by evaporation, cooling,oxidation or other means, and the film so formed may be stripped fromthe drum by means of a suitable stripping roll 4, at a point spaced fromthe point of formation of the film. The film is then wound directly intoa self-supporting roll 5 or onto a suitable reel, spool or other coreelement.

The embodiment shown in Fig. 2 is similar to that shown in Fig. 1 exceptthat in place of the large diameter drum I, there is employed an endlessbelt 6 which travels around a pair of relatively small horizontallyspaced drums la. and lb and passes upwardly around the drum in into 5contact with the flexible wall 3 of the reservoir 2 to collect a thinlayer of liquid on the outer face AI of the belt.

The layer of liquid on the carrying face AI of the belt 6 is convertedinto a m FI by passing the coated belt through a solidifying chamber 8,and the film Fl is stripped from the belt by a stripping roll 4a, andwound in a roll 5a the belt being maintained under suitable tension bymeans of the adjustable rollers 9.

The use of the belt 5 traveling around the small diameter drum Ia pastthe reservoir 2, has the advantage of .causing the liquid, shortly afterapplication to the belt, to pass from a substan-- tiaily verticalposition to a horizontal plane, thus reducing the formation of flowlines therein That embodiment shown in Fig. 3 is similar to theapparatus in Fig. 2 with the exception that instead of a belt, a fllm F2is formed on one face A2 of a web III of sheet material, taken from aroll II. The web III is passed upward around a drum I0, and after beingcoated, it is passed over a horizontal support I2 on which the layer ofliquid is converted into the film F2 and the sheet material I carryingthe film F2 is then wound on a reel b. Instead of the rigid support I2of the type shown in Fig. 3, there may be used an endless belt tosupport the sheet III in a horizontal plane during the formation of thefilm F2. The apparatus may be enclosed in a chamber 8a.

The liquid reservoir employed in each of the apparatuses shown in Figs.1, 2 and 3 comprises, in one embodiment as shown in Fig. 4, a rigidsupporting or floor plate 20 which is preferably disposed at an angle tothe film-receiving surface A, Al or A2, as shown, leaving a space Stherebetween of a width, for example, of from to 1' inch between theedge of the plate 20 and the filmreceiving surface of the drum I, belt6, or sheet I0, as the case may be.

The reservoir 2 has at least one liquid-retaining wall 3 which, as shownin Fig. 4, preferably comprises a flexible, and in some instanceselastic, liquid-retaining sheet of suitable material I2 supported, inpart, on the base or floor plate 20 and having a width greater than thecombined widths of the plate 2|! and space S, so that it is curvedupwardly to form the wall 3 which lies against the surface A, AI A2 ofthe drum I, belt 8 or sheet III, as the case may be, the flexible wall 3being maintained in this position by the upward movement of the drum Iand the hydrostatic pressure of the liquid in the container 2, while thesheet I3 asa whole is supporting the body of liquid L.

The sheet I3 may be maintained in position on the floor plate 20 bymeans of a top plate 20a which may be caused to press the sheet I3against the base plate 20 by means of screws 22. The plates 20 and 20aand the sheet material I3 extend across part or the full width of theface of the drum, sheet or belt.

As shown in Fig. 5, the ends of the reservoir of Fig. 4 are closed bymeans of relatively movable dams 23, the lateral distance between thedams being adjusted by suitable means, for example, as a telescopic rod2| having its opposite ends respectively secured to said dams, said rodbeing provided with a set screw 26. The ends I3a of the sheet I3 areextended beyond the dams reservoir on a horizontal line disposed belowthe elevation below that of the. remaining walls of 23 and may be turnedup and sealed to the outer faces of the dams, to make a liquid-tightcontainer.

As shown in Fig. 5, the upper edge 31! of the flexible wall 3 is cutaway longitudinally of the the reservoir 2, and below the operatinglevel of the film-[forming liquid L, which level is indicated by thebroken line H.

The film-forming liquid L may be introduced through a pipe 38 and thelevel a:-:c maintained by suitable means, such as an overflow pipe 40which is positioned a predetermined distance above the effective weiredge 3-8 of the flexible wall 3. The area to be coated is controlled bythe width of the weir edge 38 of the wall 3, as designated W in Fig. 5.

The liquid reservoir may be considered as a means for resilientlysupporting the liquid L, comprising the end walls formed by the dams 23,the bottom and side wall formed by the flexible sheet I3, supported bythe base plate 20, and the flexible wall 3 formed by the curved upturnedportion of the flexible sheet I3. During operation, a continuation ofthis latter wall is formed by the surface A, Al or A2, as the case maybe, which is being coated.

Whenever the liquid L contains a volatile organic solvent, it may bedesirable to prevent the evaporation of the solvent from the surface ofthe liquid L while it remains in the reservoir. Accordingly, as shown inFig. 4, a second sheet 33 of liquid-impermeable material may be insertedin between the plates 20 and 20a, the sheet 33 being narrower than thebase sheet I3 so that it floats on the surface of the liquid.

That embodiment of the reservoir .shown in Fig. 6 comprises atrough-like vessel 2a of which one side wall 40 is cut awaylongitudinally and there is attached to this wall, by suitable adhesiveor by other conventional means, a narrow sheet 3a of flexible material,this sheet being sufficiently high at the ends of the trough to completethe wall 40 and prevent the escape of liquid, the major central portionof the sheet being cut away so that the top edge 38a. of the flexiblewall formed by the sheet 3a is normally below the operating level .1: ofthe liquid in the reservoir. By mounting this trough upon a pivot rod 2|at the base of the wall 40, the coating may be discontinued by merelylowering the trough to the position indicated by the broken line,whereupon the level of the liquid will fall below the top edge 38a ofthe wall 3a.

That embodiment of the reservoir shown in Fig. 7 comprises a metalcylinder 2b mounted on an eccentric shaft 42, a longitudinal opening 43being provided in the wall of the cylinder. Th longitudinal opening 43is partly closed by a sheet I3b of flexible liquid-impermeable material.By rotating the cylinder 2b, the level of the liquid therein maybebrought to a level above the top edge 38!) of the flexible wall 3b andsimultaneously brought in contact with the surface to be coated, such asthe drum I.

The invention is not limited to an apparatus for coating a singlesurface only of a sheet material, but may be readily adapted for coatingboth surfaces thereof, and the sheet material may be in the form of anendless band or a long web. For example, there is shown in' Fig. 9, oneembodiment of suitable means for forming a film on both sides of a sheetmaterial. In this embodiment a reservoir 2, similar in construction tothose shown in Figs. 4, 6 or '7, is disposed on either side of a sheetIlla of suitable material and the sheet Illa is passed upwardly betweenthe flexand the sheet Illa, carrying assaaoa ible walls 8, 8 of thereservoirs I. 2. The sheet material Ila is maintained in the tion bymeans of the guide rollers II, II and it. the films F3, F4, passedupwardly through a vertical chamber lb for a sufficient distance toenable the film F3 and F4 on the opposite surfaces of the sheet Ila tobe converted to a non-tacky condition before the film on the one sidecontacts the upper supporting roll i9. when the apparatus is not in use,the, flexible walls I, 8 of the opposed reservoirs 2, 2 lie against andsupport each other and are thus maintained in proper position.

It is characteristic of all embodiments of the present apparatus shownin Figs. 1 to 7 inclusive, for example, that the surface to be coatedbears against the flexible wall of the reservoir and sup-' ports thiswall against the hydrostatic pressure of the liquid contained in thereservoir. For this reason it may be desirable to maintain the depth ofthe liquid in the reservoir as low as possible. and this is accomplishedin the embodiments illustrated by making the reservoir correspondinglyshallow. Since the liquid is drawn from the reservoir by contact withthe surface being coated, a great depth of liquid is not required;

In operation, as the surface A, Al etc. to be coated moves upwardly incontact with the flexible wall 3 of the reservoir 2 said wall tends tobe, bent upwardly by the upward movement of the film-receiving surfaceand is supported thereby. The hydrostatic pressure of the liquid L inthe exact central posireservoir 2 forces the flexible wall into firmconforming contact with the upwardly moving filmreceiving surface A, Al,etc. Next, the surface to be coated makes contact with the liquid L,above the weir edge 38 of the wall 3, and as this surface continues tomove upwardly it will be coated with a uniform layer of the liquid L. Asthe coated surface continues to advance, the liquid layer i' thereon isconverted into the solid film F as above described.

For the flexible wall 3 of-the reservoir 2, there may be employed anysuitable flexible sheet material which is impervious and inert to thefilmforming liquid held in the reservoir. .With aqueous film-formingliquids, there is employed a hydrophobic sheet material such, forexample, as a sheet of moisture-proof regenerated cellulose, a sheetformed of solvent-soluble cellulose derivatives as a class, organicsolvent-soluble synthetic resins'as a class, synthetic and naturalrubber, and mixtures thereof, or a fibrous sheet material such as paper,fabric, and felts coated with such hydrophobic materials. 0n the otherhand, with non-aqueous organic film-forming liquids, there is employed asheet material inert thereto such, for example, as a hydrophilic sheetmaterial, such as non-moisture-proof regenerated cellulose, gelatin,casein, hydrophilic cellulose ethers, and the like, or a fibrous sheetmaterial such as paper, fabric, or felt coated with such hydrophilicmaterials or with dextrin, starch, and the like. With both aqueous andnon-aqueous film-forming liquids there may be used a non-porous papersuch as glassine, or a fabric paper or felt provided with a continuouscoating of an insoluble thermo-setting resin or a flexible metal foil.Since the flexible sheet 3 is relatively inexpensive, it may readily bereplaced; therefore, it is not objectionable if it becomes slightlysoftened by the liquid in the reservoir.

It is to be understood that the thickness of the film formed will be afunction of the speed of the surface being coated and the viscosity ofthe liquid. Liquids of low viscosity will form thinner films thanliquids of high viscosity when the speed of the surface is constant. Onthe other hand, with a liquid of constant viscosity. thicker films willbe formed by slower movement of the casting or film-receiving surface,and thinner films by a more rapid movement of such surface. Since thereare two factors aflecting the thickness of the film, it is possible tovary the thickness over a wide range.

The thickness of the film will be determined also in part by the surfacetension of the filmforming liquid and by the roughness and porosity ofthe surface being coated.

when coating with apparatus of the type shown in Figs. 1, 2 and 3, theelevation of the reservoir with respect to the horizontal axis of thedrum I, la etc. is a factor. In Fig. 1 it will be noted that thereservoir is positioned in substantially the same horizontal plane asthe axis of the drum i, whereupon the layer l' of liquid picked up bythe surface A of the drum I, and which ultimately becomes the film Fmoves for a considerable distance through a substantially vertical path.Under these conditions, the effect of viscosity and surface tension playa more important role than the speed of the drum. On the other hand,when the reservoir is positioned substantially above the horizontal axisof the drum I, In or ib as shown in Fig. 3, the filmforming layer ofliquid i rapidly passes into a horizontal plane, so that the speed ofthe casting surface becomes relatively more important in efiecting thethickness of the film than the viscosity or surface tension.Thereservoirs of the type shown in Figs. 6 and 7 may be positioned belowthe horizontal axis of the drum I, in, etc.

For film-forming liquids which have low surface tension but a relativelyhigh specific gravity, it is desirable to position the reservoir abovethe horizontal axis of the drum as shown in Fig. 3, in order to minimizethe tendency of the liquid to develop streaks and droplets due togravity. With very viscous liquids or liquids of high surface tension,the reservoir. may be positioned as shown in Figs. 1, 6 and 7.

Solutions of certain synthetic resins and organic solvent-solublecellulose derivatives dissolved in a volatile organic solvent arefrequently characterized by exhibiting a rapid skinning effect whichresults from the evaporation of the solvent at the outer surface of theliquid layer I and the formation of a thin gel film thereon which trapsthe remaining solvent in the body of the layer I and the resulting fllmF. when this occurs, forced evaporation of solvent through the skinsurface of the film frequently results in objectio-nable pin holes andblisters. To avoid these defects, the apparatus as shown in Fig. 3 isenclosed in a drying chamber 8a which is divided into two sections MIand M2 by a partition 29. The forward chamber aai may be considered asthe film-forming chamber, and the'rear chamber 8a2 may be considered asthe film-drying chambar. There is preferably maintained in the chambertill a high concentration of the solvent used in the film-formingcomposition, and the atmosphere, as well as the surface being coated, ispreferably heated so that the solvent is only slowly evaporated from thefilm. In this way; the liquid layer I and resulting film F may be causedto form a solid uniform gel throughout its thickness. The gelled filmthen passes through the chamber to! where the remaining solvent isevaporated and the film hardened. The chamber in! may aesaeoa 9 beheated by conventional means, such as a plurality of infra-red lamps 30.

When the apparatus is used for coating fabrics, felt and porous papers,there will be, in general, substantially no tendency of the coated sheetmaterial to curl during drying. On the other hand, when relativelynon-porous sheet materials, such as calendered paper, glassine,Cellophane, a nonfibrous film, are coated on one side only, there isusually a tendency of the edges of the coated sheet material to curlinward toward the coated surface. To prevent such curling, thesupporting platform I2, as shown in Fig. 3, may be provided with anupper surface which is arcuate longitudinally and/or horizontally. Whentension is applied to the reel b, the coated sheet will be preventedfrom curling as it passes over the platform l2.

When the apparatus is to be used for forming self-supporting films, thesurface on which the film is cast may be an endless surface 6, as shownin Figs. 2 and 10, or a long web II) as shown in Fig. 3.

The operation of forming the film and ofadhering the formed film toanother surface may be carried out simultaneously by using apparatus ofthe type illustrated in Figs. and 11. In Fig. 10 there is shown suitable'means for laminating sheet materials by the use of the film formed inthe apparatus of the invention. Thus, at the exit end of the dryingchamberilb, there is disposed a pair of pressure rollers 32 and 32a, sothat the sheet material Illa carrying the film F5 on its upper surfaceis brought into contact with another sheet material lflb which may beunwound from a reel 34 and passed between the pressure rollers. Thecomposite laminated material (llia-i-F5+l0b) may then be wound up on thereel 5a. The adhesion of the two sheets may be effected before or aftercomplete drying of the film. After complete drying, adhesion is effectedby heating the film to the adhesive stage.

The apparatus of the invention is especially adapted, however, for theformation of thermoplastic transfer films and their use for coating andfinishing. There is shown in Fig. 11 one embodiment of apparatus forthis purpose, in

which the endless belt to is coated with a film F6 by means of thereservoir 2 as it passes around the drum le, the film F6 depositedthereon being dried in the chamber 80 and then passed through the heatedpressure rollers 32b and 320. A sheet material we to be coated isunwound from the reel Ho. The sheet lllc is preheated by surface contactwith the upper roller 32a, and then caused to adhere to the film F6 bypassing both between the nip of the rollers 3211-320. As a result of theheat and pressure, the thermoplastic film F6 is caused to adhere to thesurface of the sheet material file, after which the assembled sheets arecooled as in the chamber 3|. Then the belt 6a is stripped from thecoated sheet material F6 by means of a stripping roll 36, the coatedsheet material being wound on a reel 5d.

While the invention has been described with reference to the use of areservoir 2 which extends substantially the entire width of the drum,sheet or belt, on which the film is formed, it is to be understood thatby moving the dams 23 closer together, as when the sheet 63 is of anelastic nature, the liquid reservoir may be confined to anypredetermined portion of the width of the drum, sheet or belt.

By using a plurality of dams 23 with a common flexible wall, a pluralityof separate liquids may be simultaneously applied in strips onpredetermined areas of the surface being coated. In this manner, theremay be produced a composite film or coating comprising a multiplicity oflongitudinal striations which may differ from each other in chemicalnature, thickness, color or opacity.

In an alternative embodiment, the tacky surface of the freshly formedfilm may be decorated by scattering effect materials thereon, such as,for example, comminuted metallic powders, pigments, dyestuffs, and shortfibres of the same or diil'erent colors. The invention contemplates thatthe film, as it passes from the drying operation, may still be in asurface tacky condition which will facilitate the adhesion of the filmto another sheet material or to itself for building up compositearticles.

By way of illustration but not by way of limiting the invention, therewill be given the following examples:

Eazample I A solution of an ammonia-preserved natural rubber latex iscast into a film on a heated drum by means of the apparatus shown inFig. 1 using a flexible sheet of cellulose acetate as the flexible wallof the latex reservoir.

Example II Using the apparatus of Fig. 2, the flexible wall of thereservoir is made of a non-fibrous film of cellulose acetate-butyrate,and the endless belt is formed of a fabric coated with celluloseacetate-butyrate. The belt is coated with gelatin, and after passingthrough the drying chamber the film is stripped from the belt and usedas a wrapping material.

Example III Using the apparatus of Fig. 3, the flexible wall 3 of thereservoir is made of a sheet of non-moisture-proof regeneratedcellulose, and an endless web ll) of non-moisture-proof regeneratedcellulose is passed around the drum i and coated with a molten mixtureof wax and rubber. After passing through the cooling chamber to hardenthe coating, the coated film is used as a moistureproof wrappingmaterial.

\ Example IV Using the apparatus of Fig. 9, the flexible wall of thereservoir is made of a sheet of calendered paper coated with aninfusible urea-formaldehyde resin. The liquid coating compositioncomprises polyvinyl acetate dissolved in a mixture of acetone andalcohol. A web of uncoated paper is passed around the drum l and coatedwith the polyvinyl acetate solution. The film is dried, and a second webof paper is brought into con tact with the film while it is still in atacky condition. Upon the application of heat and pressure, the twosheets of paper are laminated together to form a, composite sheetmaterial.

The present invention provides an apparatus for forming uniform filmsfrom liquid filmforming materials without the limitations imposed onsuch materials by the use of wicks and doctor blades employed in priordevices. The present apparatus permits a wide latitude in the range ofviscosity and in the nature of the surface to be coated. In particular,it is possible in the present apparatus to coat sheet materials whichare so rough and irregular that they candoctor blades or other priorequipment which requires contact between the surface and the rigidelement. It is also possible with the present invention to coatcorrugated or crepe materials which cannot be coated with such priordevices. The present apparatus permits the formation of extremely thinfllms of uniform thickness by relying chiefly upon the physicalproperties of the'fllm-forming liquid rather than upon micromaticadjustments of mechanical elements.

Since certain changes may be made in the apparatus illustrated anddescribed herein. without departing from the scope of the invention, itis intended that all matter contained in the above description or shownin the accompanying drawings shall be interpreted as illustrative andnot in a limiting sense.

For example, as shown in Fig. 8, the reservoir 26 may be of a rigidwalled construction with one wall lid lying adjacent a film-receivingsurface A8 with its top edge disposed in a predetermined horizontalplane lower than the top edges of the remaining walls of the reservoir.and this lower wall may be provided with a hollow resilient seal formingelement 3d which together therewith will form the resilient wall orresilient weir 38d of the reservoir, over which an upper component ofthe body of liquid L contained in the reservoir would normally be freeto flow, in a predetermined channel formed by and between the end walls23d of the reservoir. However, the flowable component of liquid L istransversely intersected by the upwardly moving film-receiving surfaceA8 with which the component liquid contacts and adheres by surfacetension, as the surface All passes upwardly.

. Downward seepage of the liquid disposed above the weir 38d would beprevented by the resilient element 3d conforming to the surface A8,below the liquid overlying the weir 38d. This conformity may bemaintained by fluid pressure filling the hollow element 3d and derivedfrom any available pneumatic or hydraulic pressure source, including orother than the hydrostatic pressure of the liquid L in the reservoir 2d.

The pressure of the fluid within the hollow seal-forming element 3d maybe regulated by any suitable means (not shown), in accordance with theviscosity and other characteristics of the liquid L and the character ofthe surface Al in order to avoid undue pressure being exerted againstsaid surface.

Thus it will be seen that the foregoing disclosures may give use tovarious other ways and means of attaining the result of this inventionwithout departing from the spirit thereof.

I claim:

1. An apparatus for forming films from a flimforming liquid, comprisinga reservoir including an upright longitudinal flexible side wall havingan upper horizontally extending terminal edge and an adjacent marginalarea parallel thereto adapted to function as a flexible weir, and meansfor moving a film-forming surface upwardly in contact with and beyondsaid weir to engage a body of said liquid overlying said weir, said weirbeing adapted to be flexed and maintained in conforming relation to saidsurface by hydrostatic pressure of a body of said liquid containedwithin said reservoir by said flexible side wall behind and below saidweir.

2. An apparatus for forming films from a liquid film-forming materialcomprising reser- 12 voir including one upright flexiblesurface-conformable liquid-retaining wall, and means for moving afilm-receiving surface upwardly in contact with and beyond said flexiblewall with the level of the liquid in said reservoir above the top edgeof said flexible wall, one upright face of said wall being adapted to bepressed into conforming contact with said surface by lateral pressureexerted by said liquid against the opposite upright face of said wall.

3. An apparatus for forming films from a liquid film-forming material,comprising a reservoir including one upright flexiblesurface-conformable liquid-retaining wall, means comprising a rotatabledrum for moving a film-receiving surface upwardly in contact with andbeyond said flexible wall. one upright face of said wall being adaptedto be pressed into conforming contact with said surface by lateralpressure exerted by-said liquid against the opposite upright face ofsaid wail, means for maintaining the level of the liquid in saidreservoir above the top edge of said flexible wall, and side portions onsaid flexible wall extending upwardly beyond said liquid for determiningthe effective width of the film formed on said surface.

'4. An apparatus for forming films from liquid compositions, comprisinga reservoir for said liquid including at least one upright wall formedof a flexible liquid-retaining surface-conform able sheet material, arotatable drum positioned adjacent said flexible wall. and an endlessbelt passing around said drum and upwardly with its outer surface incontact with said flexible wall, one upright face of said wall beingadapted to be pressed into conforming contact with said surface bylateral pressure exerted by said liquid against the opposite face ofsaid wall.

5. An apparatus for forming fllms from liquid compositions, comprising areservoir for said liquid including at least one upright wall formed ofa flexible surface-conformable liquid-retaining sheet material. meansfor moving a sheet material to be coated upwardly with a surface thereofin contact with said flexible wall, one upright face of said wall beingadapted to be pressed into conforming contact with said surface bylateral pressure exerted by said liquid against the opposite face ofsaid wall with the level of the liquid in said reservoir slightly abovethe top edge of said flexible wall whereby the liquid contacts theupwardly moving sheet material and adheres thereto by surface tension.and means for solidifying the liquid on said surface. 1

6. An apparatus for forming films from liquid compositions. thecombination of a reservoir for said liquids having at least one uprightwall formed of a flexible surface-conformable liquidretaining sheetmaterial, a rotatable drum positioned adjacent said flexible wall, meansfor passing a sheet material upwardly around said drum with afilm-receiving surface of the last 2,4saso2 of a flexiblesurface-conformable liquid-retaining sheet material, a rotatable drumpositioned adjacent said flexible wall, means to pass a sheet materialaround the periphery of said drum upwardly in contact with said wall,one upright face of said wall being adapted to be pressed intoconforming contact with said surface by lateral pressure exerted by saidliquid against the opposite face of said wall with the liquid in saidreservoir at a level above the top edge of said wall, a chamberenclosing said drum and reservoir, and means for drying the liquiddeposited on said sheet material while it passes through said chamber.

8. An apparatus for forming films from liquid compositions, comprising areservoir for said liquid including at least one upright wall formed ofa flexible surface-conformable liquid-retaining sheet material, arotatable drum positioned adjacent said flexible wall, means to pass asheet material around the periphery of said drum upwardly in contactwith said wall, one upright face of said wall being adapted to bepressed into conforming contact with said surface by lateral pressureexerted by said liquid against the opposite face of said wall with theliquid in said reservoir at a level above the top edge of said wall, achamber divided into two compartments, one of said compartmentsenclosing said liquid reservoir and said drum and the other compartmentcommunicating with the first compartment and provided with means fordrying the deposited liquid into a film.

9. An apparatus for forming films from liquid compositions, comprising areservoir for said liquid including at least one upright wall formed ofa flexible surface-conformable liquid-retaining sheet material, arotatable drum positioned adjacent said flexible wall, means for passinga sheet material around said drum upwardly with a film-receiving surfacethereof in contact with said wall, one upright face of said wall beingadapted to be pressed into conforming contact with said surface bylateral pressure exerted by said liquid against the opposite face ofsaid wall with the liquid in said reservoir at a level above the topedge of said wall, and an elongated support positioned with one endadjacent said drum and at an elevation closely adjacent the upper partof said drum for receiving the film-laden sheet from said drum and overwhich said filmladen sheet passes with the uncoated surface thereof incontact with said support.

10. An apparatus for forming films from liquid Number compositions,comprising a reservoir for said liquid including at least one uprightwall formed of a flexible surface-conformable liquid-retaining sheetmaterial, a rotatable drum positioned adjacent said flexible wall, a.horizontal support positioned adjacent said drum and at an elevationclosely adjacent the upper part of said drum, said support having anarched upper surface, and means for passing sheet material around saiddrum upwardly with one surface thereof in contact with said wall and forpassing the said sheet from said drum and along said support with theopposite uncoated surface of said film-laden sheet in contact with saidsupport, one upright face of said wall being adapted to be pressed intoconforming contact with said sheet surface by lateral pressure exertedby said liquid against the opposite face of said wall.

11. Apparatus for forming films from a liquid film-forming material,comprising a reservoir for such liquid material, said reservoirincluding an upwardly extending wall laterally movable relative to therest of said reservoir; and means for moving a film receiving surfaceupwardly in contact with and beyond the top edge of said wall with thelevel of said liquid material above said top edge, said top edge beingdisposed adjacent said surface, the pressure of the liquid material insaid reservoir moving said wall laterally toward said surface andserving to maintain said top edge in firm engagement with said surface.

mark

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date Weston et al Aug. 14, 1928 Bates May 12,1931 Wheelwright Mar. 12, 1918 Lynah May 29, 1917 Williams Jan. 19, 1937Edwards Nov. 12,1889 Destribats Sept. 5, 1913 Kremer Mar. 14, 1916McTuitty Aug. 23, 1921 Jury May 6, 1930 Flynn Jan. 6, 1942 Murphy Aug.30, 1938 Buck Sept. "1, 1943

